It is known that cholesterol derivatives have a variety of physiological actions and that they are currently used in a variety of fields such as medicines, foods, drinks and feeds. For example, the following Patent Document 1 discloses anti-obesity agents and lipid metabolism improvers containing 24-alkylchlestane-3-one or 24-alkylchlestene-3-one as an active ingredient. In addition, the following Patent Document 2 discloses anti-obesity agents and lipid metabolism improvers containing as an active ingredient 24-methylcholest-5-ene-3-one which is a 5-ene-3-one derivative of sterol. Further, it is known that, in comparison with a 4-ene-3-one derivative of sterol, a 5-ene-3-one derivative and a 3,6-dione derivative of sterol are superior in terms of obesity and lipid metabolism-correctional mechanisms.
As well a chemical synthesizing method, a biological method of synthesizing a cholesterol derivative by culturing a microorganism is also known. As a biological synthesizing method of synthesizing a cholesterol derivative, for example, the following Non-Patent Document 1 discloses that a cholest-4-ene-3-one is obtained with cholesterol oxidase which is an enzyme using cholesterol or a derivative thereof as a substrate. According to this method, a 5-ene-3-one derivative is obtained by means of an oxidizing reaction from cholesterol, or a derivative thereof, which serves as a substrate, and then, a 4-ene-3-one derivative is rapidly produced by means of an isomerization reaction. And, the following Non-Patent Document 2 describes a method of biologically converting cholesterol into cholest-4-ene-3-one by using a microorganism (ARTHROBACTER) of a nature that is capable of producing cholesterol oxidase in a bilayer system of an aqueous layer and an organic solvent.    [Patent Document 1] JP-A-11-193296    [Patent Document 2] JP-A-2001-240544    [Non-Patent Document 1] “Bioscience and Industry” Vol. 57 No. 7 ('99) 464-467    [Non-Patent Document 2] “Enzyme and Microbial Technology” 1996, Vol. 18:184-189